I think they do it on purpose, it's only just ukraine, why waste your best equipment for it? why potentially give away military secrets in case they are getting captured by NATO

Both the US and France made the mistake to send their best weapons, only for them to get sold in black market, and then Russia managed to buy them, they now reverse engineered them and are able to detect and counter US/FR missiles

Hence the reason why the US is now against sending most of their weapons, too late

https://www.reuters.com/world/europe/us-will-not-send-ukrain...